1. Field of the Invention
The present invention relates to synergistic antimicrobial compositions which are generally useful for inhibiting microbial growth wherever such microbial growth is found, for example, in aqueous systems related to a wide variety of industrial applications. More particularly, the present invention relates to synergistic admixtures of 2,4,4'-trichloro-2'-hydroxydiphenyl ether and 1,2-dibromo-2,4-dicyanobutane. Methods for using the same are also disclosed.
2. Description of the Background Art
Both 2,4,4'-trichloro-2'-hydroxydiphenyl ether, referred to herein as Triclosan, and 1,2-dibromo-2,4-dicyanobutane (DBDCB), are known individually as antimicrobial agents. The unexpected finding of the present invention is that they are synergistic when used in combination. As used herein, the terms "synergy" and "synergistic" refer to instances where the effectiveness of a composition comprising two or more biocides, such as Triclosan and DBDCB, exceeds the sum of the efficacies of the individual components taken alone. Thus, using a synergistic biocidal combination may allow for use of a lower overall concentration of biocide or the realization of an enhanced antimicrobial effect at a comparable dosage.
U.S. Pat. Nos. 3,833,731, 3,877,922, 3,873,597, 3,644,380, 3,833,743, and 3,929,858 disclose DBDCB and its use as an antibacterial, antifingal, and algicidal agent. Compounds related to DBDCB are also effective as antimicrobial agents. For example, U.S. Pat. No. 4,442,122 describes the use of 1,2-dibromo-2-cycloalkane compounds to inhibit microbial growth, and U.S. Pat. No. 4,496,581 discloses 1,2-dibromo-2-cyano-2-(heterocyclic) alkane compounds and their use as antimicrobial agents.
The use of DBDCB and related compounds in conjunction with other antimicrobial agents is also known in the art. U.S. Pat. No. 4,604,405 describes a synergistic antimicrobial composition for industrial and agricultural use comprised of DBDCB and 2,2-dibromo-3-nitrilopropionamide. U.S. Pat. No. 4,655,815 discloses a synergistic antimicrobial admixture comprising DBDCB and a formaldehyde donor. U.S. Pat. No. 4,830,657 describes a synergistic antimicrobial combination comprising DBDCB and 1,2-benzisothiazolin-3-one. U.S. Pat. No. 5,034,405 discloses the use of admixtures of DBDCB, 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one as antimicrobial agents. U.S. Pat. No. 5,124,355 discloses an antimicrobial composition of DBDCB and 2-(decylthio) ethaneamine and a method of using the same. U.S. Pat. No. 5,364,874 discloses a composition containing 2-halo-2-halomethylglutaronitrile and a 4,5-polymethylene-4-isothiazolin-3-one which has antibacterial and antifungal effects.
Likewise, the use of 2,4,4'-trichloro-2'-hydroxydiphenyl ether and related compounds, both alone and in conjunction with other biocides, is known. The synergistic combination of Triclosan and DBDCB, however, is not taught or suggested in the art.
As used herein, the phrases "antimicrobial", "biocide", and "inhibiting microbial growth" refer to the killing of, the inhibition of, or the control of the growth of bacteria, yeast, mold, and/or algae. A number of important industries have experienced serious adverse effects from the activity of such biological growth on the raw materials which they employ, in their process waters, on various components of their manufacturing processes, and in the finished products which they produce. Such industries include the paint, wood, textile, cosmetic and personal care, leather, tobacco, fur, rope, paper, pulp, plastics, fuel, oil, rubber, and machine industries.
It is contemplated that the synergistic admixture of Triclosan and DBDCB as disclosed herein, and the methods for using the same, will be useful in virtually any aqueous system or on any article or product of manufacture in which inhibition of microbial growth is desired, absent compatibility problems. Important applications of the synergistic antimicrobial combinations of the present invention include, for example: inhibiting the growth of bacteria and fungi, including yeast and mold, in aqueous paints, adhesives, latex emulsions, inks and joint cements; preserving wood; preserving cutting oils and metal working fluids; controlling slime-producing bacteria and fungi, including yeast and mold, in pulp and paper mills and cooling towers; as a spray or dip treatment for textiles and leather to prevent mold growth; as a component of anti-fouling paints to prevent adherence of fouling organisms; protecting paint films, especially exterior paints, from attack by fungi which occurs during weathering of the paint film; protecting processing equipment from slime deposits during manufacture of cane and beet sugar, foods, foodstuffs and food additives; preventing microorganism buildup and deposits in air washer or scrubber systems and in industrial fresh water supply systems; controlling microorganism contamination in closed loop and recirculating water cooling systems; controlling microorganism contamination and deposits in oil field drilling fluids and muds, and in secondary petroleum recovery processes; preventing bacterial and fungal growth in paper coating processes which might adversely affect the quality of the paper coating; controlling bacterial and fungal growth and deposits during the manufacture of various specialty boards, e.g., cardboard and particle board; preventing sap stain discoloration on freshly cut wood of various kinds; controlling bacterial and fungal growth in clay and pigment slurries of various types which are manufactured for later use in paper coating and paint manufacturing and which are susceptible to degradation by microorganisms during storage and transport; as a hard surface disinfectant to prevent growth of bacteria and fungi on walls, floors, etc.; and in swimming pools to prevent algal growth.
The synergistic antimicrobial composition disclosed in the present invention is particularly applicable to the control of bacterial and fungal growth in cosmetic and personal care products. Such products include but are not limited to creams, lotions, shampoos, conditioners, sunscreens, hand cleaners, liquid hand soaps, detergents, hospital scrubs, bactericidal washes, deodorants, and the like. Cosmetic and personal care products subject to microbiological attack can suffer from separation of emulsions, discoloration, unsightly visible colonies, malodor, and change of pH; microbial growth in these products can also lead to potential health hazards.
Accordingly, there remains a very real and substantial need for antimicrobial compositions capable of effectively controlling and/or inhibiting microbial growth in industrial aqueous systems and in articles of manufacture. Because of increasing environmental regulations, there is still a further need to provide biocidal compositions having enhanced antimicrobial effect which are effective in lower doses than historically used. Use of lower amounts of biocides has a favorable impact on the environment, and allows users to realize significant cost savings.